Method, apparatus, and elements thereof for use in the electrodeposition of chromium



oct. 2, 1934. C. H ELDRmGE 1,975,227

METHOD, APPARATUS, AND ELEMENTS THEREOF FOR USE IN THE ELECTRODEPOSITIONOF CHROMIUM Filed Jan. 51, 1951 FIG.. Z Y Fla?) ((/DNLINVENTOR EYPatented Oct. 2, 1934 METHOD, APPARATUS',

AND ELEMENTS THEREOF FOR USE IN THE ELECTRO- DEPOSITION OF CHROMIUMCharles H. Eldridge, Detroit, Mich., assignor to United Chromium,Incorporated, New York, N. Y., a corporation oi' Delaware ApplicationJanuary 31, 1931, serial No. 512,579

7 Claims. (Cl. 20d-5) This invention relates to apparatus and elef mentsthereof for use in the electrodeposition of chromium and providesimprovements therein.

As is well recognized in the art of chromium deposition, a want existsfor apparatus (tanks,

coils, anodes, etc.) more serviceable than that heretofore available andsuitable for common use.

Ceramic and glass apparatus and elements are used, but these are fragileand limited as to size. 10 Iron apparatus and elements have been used,but

the iron dissolves and objectonably contaminates the bath. Leadapparatus and elements (the term being used herein to cover lead,inclusive of antimony lead, lined apparatus) have been 5 most commonlyand generally used in the electrodeposition of chromium. Lead apparatusand relements have some drawbacks, as they require special care`(whichis not always known and given) to prevent perforation due to the attackthereon of acids and acid radicals contained in the bath-the commonlyused baths containing chromic acid and acid radicals in quantity andrelative amounts which have such attack. Another drawback is theencrustation of the parts with sulphates and chromates, which olerresistance to the ow of current (particularly anodes) and resistance totemperature interchange (heating and cooling coils). Then from time totime there are unexplained failures with lead apparatus, and renewalsand replacements are expensive, and there are other drawbacks.

By the present invention I provide an apparatus and elements thereofwhich is much more resistant to attack by chromium plating solutions,and which will give superior service to lead apparatus and elements andavoids much of the special care required for preserving the latter.

The invention provides apparatus and elements 4thereof which may beformed with substantially 40 the same facility and exibility and bysubstantially the same methods as lead apparatus and elements, and whichmay have the advantage of greater rigidity (while still maintainingductility) than even the lead known as hard lead.

Lead anodes used in the electrodeposition of chromium are especiallysusceptible to attack, and the present invention provides anodes whichare much less susceptible to attack than such 50 lead anodes.

An embodiment of the invention is illustrated in the accompanyingdrawing, wherein:

Figure l is a top plan view of an apparatus for the electrodeposition ofchromium and em- 55 bodying the present invention.

Fig. 2 is a transverse vertical section, drawn on twice the scale ofFig. 1.

Fig. 3 is an enlarged detail view of an anode. Referring to saiddrawing, numeral 10 designates a tank or container provided with theusual or any suitable arrangement of cathode bus-bars 12,cathode-current conductor 14, anode bus-bars 16, anode-current conductor18, and suitable ducts 20. J

Numeral 22 designates the anodes, and 24 the 65 coil or coils used forcontrolling the temperature of the bath-cooling coil, heating coil orboth kinds of coils. The apparatus may comprise more or less elements ofthose mentioned and not mentioned as maybe necessary or desirable.

According to the invention the apparatus and/or its elements,particularly the parts which are immersed in the chromium-depositionbath or otherwise subjected to the action o the solution, are formed ofan alloy of lead and tin, the l5 base or predominant part of which islead.

Eenecial elects according to the invention are obtained with a tincontent as low as three percent (3%). With a tin content of ve percent(5%) and more the corrosion is practically neg- 30 ligible. Thepreferred tin content is about seven percent (7%).

Ductility and malleability sumcient for practical Aworking is maintainedwith a tin content up to and including about ten percent (10 With castparts the content of tin may exceed ten percent, but there does notappear to be any substantial advantage in materially exceeding tenpercent of tin, as both the cost and the brittleness increases withincreased tin content.

The tank 10 is preferably formed of sheet-steel (though wood or otherlow-cost material may be used) as indicated at 30, and provided with alining 32 of the hereindescribed lead-tin alloy. The lining 32 ispreferably applied in the form of duc- 95 tile and malleable sheets ofthe alloy within the hereindescribed range, and the edges may be joinedor lapped and joined by burning such as is practiced in socalledlead-burning. The coils 24 are preferably formed of extruded, or 100drawn alloy, or of strips of the alloy formed into hollow form and theedges closed by burning, the alloy preferably being within the rangehereindescribed for obtaining ductility and malleabilitywherebyxfragility is avoided.

The anode 22 is preferably made of strips of the hereindescribed alloy,and the upper end provided with the usual hook 34 by which it issuspended from the anode bus-bar 16. At the solution-line the anode ispreferably made of in- 110 creased thickness, as indicated at 36. toprovide more material against Wastage by corrosion, as it is found inchromium deposition that corrosion most readily occurs at thesolution-level.

The invention mayL receive -other embodiments than those hereinspecifically illustrated and de-` scribed.

What is claimed is:-

1. An element of a chromium plating installation which is in contactwith a chromic acid solution, consisting essentially of a lead-tin alloycontaining a minimum of approximately three per cent tin.v

1 2. An element cfa-chromium plating installation which is in contactwith a chromic acid solution, consisting essentially of a lead-tin alloycontaining approximately three to ten percent inclusive of tin.

3. An element of a chromium plating installation which is in contactwith a chromic acid solution, consisting essentially of a lead-tin alloycontaining approximately seven percent tin.

4. An anode for chromium plating in a bath containing chromic acidconsisting essentiaily of 6. An anode for chromium plating in a baths,V

containing chromic acid consisting essentially of a lead-tin alloycontaining approximately seven percent tin.

'7. In' a process ci.' chromium plating in which the bath containschromic acid, inhibiting sediment\ due to the action of the chromic acidby forming the parts of the installation which are 5in contact with thechromic acid o! an alloy essentially of lead and tin containing aminimum of approximately three percent tin.

los

